Presser lifter mechanism for sewing machines



H. RITTER May 29, 1962 PRESSER LIFTER MECHANISM FOR SEWING MACHINES Filed Feb. 12, 1959 INVENTOR. Herman Riffer BY 2 2 ATTORNEY WITNESS wzdia c w United States Patent ()fiice 3,036,535 Patented May 29, 19 62 3,tl36,536 PRESSER LIFTER MECHANISM FOR SEWING MA CHINES Herman Ritter, Cranford, N.J., assiguor to The Singer Manufacturing Company, Elizabeth, N.J., a corporation of New Jersey Filed Feb. 12, 1959, Ser. No. 792,861 1 Claim. (Cl. 112237) The present invention relates to sewing machines and particularly to the presser lifter mechanism of an industrial type sewing machine, for example, as illustrated in the United States patent of Kaier, No. 2,250,993.

Present day industrial sewing machines generally include a treadle or knee operated presser lifter mechanism that includes a presser lifter lever pivotally mounted intermediate its ends at the back of the bracket arm. The pivot for the lever must be periodically lubricated or seizing will occur so that the presser lifter becomes inoperative in that it is very diflicult to raise the presser and it will not return properly to its operative position when released. When the presser cannot return to its operative position, the feed mechanism becomes ineffective and the machine is inoperative until the pivot is freed. In addition to the attention required of the mechanic to free the pivot, this condition results in further expenses in lost time and in the spoilage of work. Since seizing is not instantaneous the machine may be operated for a considerable period of time before the operator notices that it is not feeding properly, and all this time it pro duces defective work.

Modern high speed industrial sewing machines are generally automatically lubricated. Since the presser lifter lever has a swinging motion and since it extends into the head of the machine, the pivot cannot be automatically lubricated without providing an opening into the head and thus expose the head to the oil mist inside the frame. As a result, the presser lifter lever is mounted outside the frame of the machine and must be lubricated manually even in an automatically lubricated machine. Being virtually the only part on the machine requiring manual lubrication and actually requiring lubricant only at infrequent intervals, it very often occurred that the pivot was not lubricated at all until improper functioning was noticed.

In accordance with the above it is an object of this invention to provide a presser lifter mechanism that is free from the danger of seizing of the presser lifter lever even in the absence of lubrication, is economical, and which can be applied to existing machines.

Having in mind the above and other objects that will be evident from an understanding of this disclosure, the invention comprises the devices, combinations and arrangements of parts as illustrated in the presently preferred embodiment of the invention which is hereinafter set forth in such detail as to enable thoseskilled in the art readily to understand the function, operation, construction and advantages of it when read in conjunction with the accompanying drawings in which:

FIG. 1 is a rear elevational view of a sewing machine embodying the present invention.

FIG. 2 is a fragmentary sectional view taken substantially on the line 22 of FIG. 1.

FIG. 3 is a fragmentary sectional view taken substantially on the line 3-3 of FIG. 2.

With reference to the drawings there is illustrated a sewing machine having a frame including a bed plate 1 the upper surface of which defines the work supporting surface of the machine and a standard 2 rising from one end of the bed plate 1 and carrying a bracket arm 3 terminating in a head 4 overhanging the bed plate 1. Mounted vertically in the head 4 for endwise sliding movement is a spring-depressed presser bar 5 carrying a presser foot 6 at its lower end.

During operation of the machine, the presser bar 5 is spring biased downwardly to hold the presser foot 6 in engagement with the work supporting surface of the machine. The presser foot acts in opposition to the feed dog (not shown) of the machine to hold the Work in operative engagement with the feed dog and to prevent flagging of the work. To introduce work, the presser mechanism is lifted. In the illustrated machine this is accomplished by a presser lifter mechanism including a presser lifter lever 7 arranged horizontally at the rear of the bracket arm 3. The lever 7 includes a pin 8 at the head end thereof that extends into the head 4 and is operatively connected therein to the presser bar 5. Operator actuated means is connected to the standard end of the lever 7 for imparting pivotal movement to the lever. The operator actuated means comprises a pull rod 9 connected to the end of the lever 7 and extending through the bed plate 1 where it is adapted to be connected with an operator-controlled treadle or knee-operated mechanism (not shown).

Pivot means are provided for pivotally mounting the lever 7 intermediate its ends on the bracket arm 3. The illustrated pivot means comprises a pivot stud in the form of a pivot screw 10 having a head 11, a smooth surfaced shank 12, and a reduced threaded end 13 defining a shoulder 14. The screw 10 is threaded into the rear wall of the bracket arm 3 with the shoulder 14 tightened against the outer face of the wall.

The lever 7 is pivotally mounted on the screw 10 in such a manner that there is only a limited bearing surface between the periphery of the shank 12 and the lever 7. More particularly, engagement between the lever 7 and the shank 12 is made to occur only on the upper portion of the periphery of the shank 12 while the lever is spaced from the lower portion of the periphery of the shank 12. To provide for this, the lever 7 is formed. with an open ended slot 15 extending inwardly from the bottom edge of the lever, which slot is made wide enough so that the shank 12 can pass freely therethrough. Bearing engagement occurs at the inner or upper end 16 of the slot 15, which end preferably is made arcuate or semi-cylindrical and is formed on a radius only slightly larger than the radius of the shank 12 of the pivot screw 10 so as to conform substantially to the periphery of the shank 12.

A spring is coiled about the shank 12 and has oppositely extending ends 18 and 19. The end 18 is bent at a right angle and extends into a bore in the rear wall of the bracket arm 3 to anchor the same and the end 19 is bent around the bottom edge of the lever 7 so that the spring continuously biases the lever 7 in a clockwise direction about the shank 12.

Constructed in this manner, the lever 7 is free to rock on the shank 12 of the pivot screw 10. There is a minimum of bearing engagement between the lever and the screw 10 and it is not a true rocking motion, the resulting motion of the lever 7 on the pivot screw 10 is dis tinguishable from the sliding engagement of the prior constructions and does eliminate the possibility of seizing at the pivot point even in the absence of lubrication. A true rocking motion could be obtained by reducing the engagement to a knife-like edge. However, this is not necessary to eliminate seizure and in view of the fact that it is relatively expensive and not rugged enough for use in an industrial sewing machine, the preferred construction is as disclosed. Another advantage of the construction is that, since the lower portion of the pivot screw 10 is not confined, any corrosion or other material worn from the engaging surfaces will fall away rather than accumulate and cause jamming. The resulting wear on the lever 7 serves only to enlarge the end 16 of the slot 15 so that it acts to make the connection more loose and thus still less likely to seize. It is of course obvious that an insert can be used at the bearing surface between the lever 7 and the shank 12, which insert could not only be made replaceable so that it can be renewed, but also could be made of a self-lubricating material. However, such inserts are relatively expensive and one of the advantages of the present invention is that the construction comprises a very inexpensive manner of obtaining a presser lifter lever that will function satisfactorily without seizing and without excessive wear even in the absence of lubrication. Another advantage of the present invention is that it can be readily applied to existing machines by providing a presser lifter lever in accordance with the invention or by machining an open end to the pivot hole of the present levers.

During normal operation, the forces on the lever 7, i.e., bending about the pivot screw 10 arising from the pull imparted to it by the rod 9 and the resistance at the pin 8, tend to keep the lever 7 with the shank 12 seated in the end 16 of the slot 15. The spring 17 also acts to keep the lever in assembled relation on the shank 12, which becomes important during handling of the machine.

Having thus set forth the nature of my invention, what I claim herein is:

In a sewing machine having a frame including a work supporting surface and a bracket arm overhanging said work supporting surface and terminating in a head, a vertically arranged presser bar mounted in said head for endwise movement and carrying at its lower end a presser foot that is adapted to hold the work down against said work supporting surface, and a presser lifter mechanism for raising said presser bar and thereby moving said presser foot away from said work supporting surface, said presser lifter mechanism comprising a presser lifter lever, pivot means pivotally mounting said presser lifter lever on said frame, means operatively connecting one end of said lever to said presser bar, an operator-actuated pull rod connected to the other end of said lever, said pivot means comprising a pivot stud carried by said bracket arm, and said lever having a downwardly open slot intermediate its ends for receiving said pivot stud.

References Cited in the file of this patent UNITED STATES PATENTS 608,553 Mack Aug. 2, 1898 1,699,659 Fagan Jan. 22, 1929 2,250,992 Kaier July 29, 1941 2,468,673 Kaminky Apr. 26, 1949 2,657,781 Zeidler Nov. 3, 1953 2,841,106 Althens July 1, 1958 

